1. Field of the Invention
This invention relates to a method of making dinitramide salts. More particularly, this invention relates to a method of making dinitramide salts by nitration of a carbamate.
2. Description of the Related Art
Solid oxidizers, such as ammonium perchlorate or potassium perchlorate, have been used in the past in rocket propellant formulation because of their greater stability than liquid oxidizers. However, the presence of a halogen in the solid oxidant produces a smoke trail which is observable on radar and sometimes visually as well. Also, chlorine poses a serious atmospheric environmental hazard of ozone depletion.
Because of such shortcomings in the use of perchlorate solid fuel oxidizers, other materials, including nitrate (NO.sub.3.sup.-) compounds, have been investigated in the search for oxidizers which would provide the desired energy density and stability, without the drawbacks of the perchlorate oxidants.
Hamel et al. U.S. Pat. No. 3,428,667 describes the reaction of an ionic nitronium salt with a primary organic nitramine to form N,N-dinitramines having the general formula R--N(NO.sub.2).sub.n where n is 1-2 and R is a monovalent or divalent organic radical. These compounds are said to be highly energetic and useful as ingredients in propellant, explosive, and pyrotechnic compositions.
Willer et al. U.S. Pat. No. 4,878,968 describes the formation of gun and rocket propellants which include substituted cubanes such as cubane-1,4-bis(ammonium nitrate), or 1,4-bis(ammonium)pentacyclo[4.2.0.0.sup.2.5.0.sup.3.8.0.sup.4.7 ]octane dinitrate; and cubane ammonium nitrate, or pentacyclo-[4.2.0.0.sup.2.5.0.sup.3.8.0.sup.4.7 ]-octylammonium nitrate.
Leroy et al., in "A Theoretical Investigation of the Structure and Reactivity of Nitrogen-Centered Radicals", published in the Journal of Molecular Structure (Theochem), 153 (1987) on pages 249-267, by Elsevier Science Publishers B.V. Amsterdam, The Netherlands, discusses the structure, stability, and reactivity of nitrogen-centered radicals. Listed in Table 6 are various reactions of N-centered radicals, including reactions of N(NO.sub.2).sub.2 with NH.sub.2 to form 2NHNO.sub.2, and with CH.sub.3 NHNO.sub.2 to form CH.sub.3 NNO.sub.2 and NH(NO.sub.2).
In the Third Quarterly Report on Basic Research in Solid Oxygen Oxidizers of Government Contract AF 04(611)-8549 dated December 1963, on pages 6 and 7, the reaction of nitronium tetrafluoroborate with the dianion of methylenedinitramine to form an intermediate anion is hypothesized, and it is speculated that the intermediate anion may either react with a second equivalent of nitronium tetrafluoroborate to form N,N,N',N'-tetranitromethylenediamine or undergo fragmentation to form an anion which has the formula N(NO.sub.2).sub.2.
It would, however, be desirable to provide a safe, simple, and inexpensive method of forming a stable solid ionic nitrate compound useful as a rocket propellant fuel which would have the clear advantage over perchlorates of being free of chlorine, but would be as stable as presently used perchlorate compounds and be much more stable and inexpensive than prior art dinitramine compounds.